Currently the commonest method of preparing a lithographic plate is to image a photosensitive lithographic plate using an image mask, such as a photographic negative, and to prepare the plate therefrom using an aqueous developing solution. This procedure is time consuming and requires facilities and equipment to support the necessary chemistry.
Thus recently various methods have been proposed for preparing lithographic plates on the press which is to be used to produce prints from the plate. These methods prepare the image using a digitally controlled laser image head. As described in European Patent Application 580393 such methods include ink-jet methods digitally controlled, spark-discharge methods and the production of electromagnetic-radiation pulses that create chemical changes of the plate blank. Also etching methods have been described as well as blank plates which are ablated by the laser to form an ink-receptive image. But such methods require expensive apparatus.